55A distinction must be drawn between acquired pension rights and pension amounts. The concept of ‘acquired pension rights’ refers to the pension rights resulting from the contributions paid on an individual basis by each of the applicants and which form the basis for the calculation of the retirement pension paid to them under the AVPS. That concept therefore cannot be understood as referring to an alleged right to receive a fixed and immutable pension amount calculated on the basis of the rules in force at the time when the pension is paid (see, by analogy, judgment of 19 September 2024, Coppo Gavazzi and Others v Parliament, C‑725/20 P, EU:C:2024:766, paragraph 89).